Gaseous-discharge device



April '15, 1952 K. J. GERMESHAUSEN GASEOUS-DISCHARGE DEVICE 3 Sheets-Sheet 1 Filed Sept. 25, 1947 INVENTOR. Kane J. fitrmeskaasga BY j z April 15, 1952 Filed Sept. 25, 1947 I600 I600 I400 I200 I000 600 600 400 200 K. J. GERMESHAUSEN GASEOUS-DISCHARGE DEVICE 3 Sheets-Sheet 2 aschen Curve for He/ium 2' d 4' a 24's 217M824?) 50 Pressure in mm X spacing in cm' r'zg'. 6

IN V EN TOR. lkzmeilz J fiermesllausen April 15, 1952 Filed Sept. 25, 1947 K. J. GERMESHAUSEN 2,592,556 GASEOUS DISCHARGE DEVICE 3 Sheets-Sheet 3 INVENTOR.

Patented Apr. 15, 1952 UNITED STATES PATENT OFFICE GASEOUS-DISCHARGE DEVICE Kenneth J. Germeshausen, Newton Centre, Mass. Application September 25, 1947, Serial No. 776,121

1 25. Claims.

The present invention relates to gaseous-discharge devices, and more particularly to gaseousdischarge devices of the cold-cathode, especially the Strobotron, type. The present application is a continuation-in-part of application Serial No. 646,066, filed February '7, 1946.

An object of the present invention is to provide a new and improved gaseous-discharge device, particularly of the Strobotron type, that shall be operable at high voltages with high-peak currents, particularly at high frequencies, and that shall have the advantages of ease of control and absence of cathode-heating power.

A further object is to provide novel cold-cathode arc operation in a low-pressure gaseous -discharge device of the above-described character the distance between the grid or control electrode and the anode of which shall be such that the product of the said distance and the pressure of the gas in the device shall be presented by points of the Paschen curve for the said gas to the 'left of its lowermost portion.

Another object is to provide novel cold-cathode arc operation in a low-pressure gaseous-discharge device of the above-described character the distance between the grid or control electrode and the cathode of which shall be such that the product of the said distance and the pressure of the gas in the device shall be represented by points of the Paschen curve for the said gas essentially to the right of its lowermost portion, the said distance being such as to provide a substantially minimum breakdown voltage between the control electrode and the cathode.

Another object still is to provide novel coldcathode arc operation in a low-pressure gaseousdischarge device of the above-described character provided with two control electrodes one of which shall be spaced from the anode a distance such that the product of the said distance and the pressure of the gas in the device shall be represented by points of the Paschen curve for the said gas to the left of its lowermost portion and the other of which shall be spaced from the said one control electrode a distance such that the product of this last-named distance and the said pressure shall be represented by points of this Paschen curve essentially to the right of the said lowermost portion, the said last-named distance being such as toprovide a substantially minimum breakdown voltage between the said one control electrode and the said other control electrode.

Still a further object is to provide novel cathode arc operation in a low-pressure gaseous-discharge device of the above-described character provided with a plurality of control electrodes one 2 of which shall be spaced from the anode a distance such that the product of the said distance and the pressure of the gas in the device shall be represented by points of the Paschen curve for the said gas to the left of its lowermost portion and each of which and the cathode shall be spaced from one another a distance such that the product of this last-named distance and the said pressure shall be represented by points on this Paschen curve essentially to the right of the said lowermost portion; the said last-named distance being such as to provide a substantially minimum breakdown voltage between each of the control electrodes and the cathode.

Other and further objects will be explained hereinafter, and will be particularly pointed out in the appended claims.

The invention will now be more fully explained in connection with accompanying drawings, in which Fig. 1 is a front elevation of'a gaseous-discharge device embodying the present invention, in preferred form; Figs. 2 and 3 are horizontal sections taken upon the lines 2--2 and 3-3, respectively, of Fig. 1, looking in the direction of the arrows; Fig. 4 is a vertical longitudinal section taken upon the line 4-4 of Fig. 2, looking in the direction of the arrows; Fig. 5 is a rear elevation; Fig. 6 is a graph representing fragmentary portions of the Paschen curve for helium, the abscissae representing the product of the gas pressure, in millimeters, and the spacing of the electrodes, in centimeters, and the ordinates representing the breakdown voltage between the electrodes, in volts; Fig. 7 is a diagrammatic view of a circuit with a tube of the present invention connected therein; and Fig. 8 is a similar diagrammatic view of a modification.

The illustrated gaseous-discharge tube, shown of the Strobotron type comprises an evacuated glass envelope filled with a suitable gas, at a relatively low pressure, and containing a plurality of electrodes, as follows: a solid cold cathode 2, a plurality of control-grid electrodes and an anode 5. Three control-grid electrodes are illustrated, namely, a first control-grid electrode 3, a second control-grid electrode 30 and a third control-grid electrode 4, in the form of a cylindrical spool of carbon concentric with and surrounding the anode 5. The anode 5 is provided with an anodelead conductor 2|, and the cathode 2 with par.- allel-connected cathode-lead conductors 23 and 53. The cylinder grid 4 is fixed to a grid-support element l2, in the form of a metal strap wrapped tightly around the carbon cylinder 4 and attached to a lead conductor M. The control-grid pressure,

electrodes 3 and 30 are respectively provided with lead conductors 25 and 32.

The lead conductors I4, 2|, 23, 25, 32 and 53 extend through the base 4| of the envelope I. Any of the control-grid electrodes 3, 4 and 30, or a combination thereof, depending upon the particular application, may be used for control purposes.

The cathode 2 is shown comprising a pill 8, held in place by a wire-mesh screen 9 at the bottom of a metal cup I8. The pill 8 may be constituted of compressed caesium chloride and aluminum filings or powder, or other material of low-work function, and forms the active material of the cathode.

A mica disc 22 divides the space in the envelope into a lower region, containing the cathode 2 and the grid 4, and an upper region, into which project the grids 3 and 30. The mica disc 22 is provided with an opening 29 for receiving the upper portion of the carbon cylinder 4, of reduced diameter, and an opening 45, disposed above the cathode 2, and of smaller diameter than the diameter of the metal cup of the cathode 2. Electrons from the cathode 2 may therefore travel through the opening 46 into the upper region of the envelope I and into the axially disposed opening of the carbon cylindrical spool 4 to the anode 5. The discharge therefore takes place from the lower region of the envelope I, below the mica disc 22, in the interior of the metal cup I8 of the cathode 2, into the upper region, above the mica disc 22, and back to the lower region, below the mica disc 22, to the anode 5. The presence of the mica disc 22 ensures that the discharge shall not take place directly from the outside walls of the metal cup I8 of the cathode 2 to the anode 5.

Glass or other insulating sleeves 34 and 36 surround the leads to the control-grid electrodes 3 and 30, below the mica disc 22, to prevent any discharges from occurring between the portions of these electrodes 3 and 30 below the mica disc 22, on the one hand, and the cathode 2 and the grid 4 on the other. A second mica disc 21 fits down tightly on to glass pieces I6 projecting upward from the base 4|. Any small remaining spaces below the mica disc 21 between the glass projections l6 are filled with a ceramic cement 43. This structure prevents the occurrence of any long-path breakdown discharges between the anode 5 and the outside of the grid 4 or the other elements of the tube, and assures that the breakdown shall occur along the curved arc before described between the cathode 2 and the anode 5.

In accordance with a feature of the present invention, the spacing between the grid 4 and the anode 5 inside the concentric spool cylinder 4 is such that the operation, when helium is the gas employed, is represented by the points of the lefthand portion of the Paschen curve of Fig. 6, to the left of its lowermost portion, according to which the breakdown voltage may be high even for close spacings and low pressures. As appears from this lowermost portion of this curve, the breakdown voltage between the electrodes is very low, on the order of 150 volts, and it does not vary very rapidly, with changes in pressure or spacing, over a considerable range of both pressure and spacing. As an example, for a typical tube, a pressure of millimeters of helium, and a spacing between the grid 4 and the anode 5 of 0.05 centimeter, would yield a product of 0.5. The corresponding breakdown voltage is shown in Fig. 6 to be approximately 2000. With the same low on the other hand, a spacing, between the control electrode 3 and the interior of the metal cup I8 of the cathode 2, on the order of 0.4 centimeter, would yield a product of 4 and a corresponding breakdown voltage of approximately 1'75. This spacing is not, however, very critical since, as appears from Fig. 6, the product of pressure and spacing may vary from about 1 to about 15, without appreciable changes in the breakdown voltage.

In accordance with the said feature of the present invention, therefore, the distance between the grid 4 and the anode 5 is such that the product of the said distance and the pressure of the gas in the device is represented by points of the Paschen curve for the said gas to the left of its lowermost portion, thus providing a high breakdown voltage between the grid 4 and the anode 5. The distances between other control electrodes, on the other hand, are such that the product of each of these distances and the pressure of the gas in the device is represented by points of the Paschen curve for the said gas essentially to the right of its lowermost portion, yielding a relatively low substantially minimum breakdown voltage between any of the other control electrodes or from each of these control electrodes and the cathode 2.

The hot-cathode thyratron is likewise suitable for high-voltage operation, but the peak current of hot-cathode thyratrons is limited by the hot cathode. Gaseous-discharge devices of the Strobotron type, disclosed in Letters Patent 2,185,189, 2,201,166 and 2,201,167, issued to Kenneth J. Germeshausen, on January 2, and May 21, 1940, on the other hand, though particularly adapted for operation at high-peak currents, can operate at high voltage only at excessive pressures or spacings, and these would interfere with the desired characteristics of the gaseous-discharge device.

The anode 5 is preferably constituted of a material of refractory nature, such as tungsten or tantalum, to prevent excessive sputtering of the anode under high-current-discharge conditions. This sputtering, if excessive, would result in the disappearance of the gas in the tube. The use of tungsten for an anode, as compared to nickel, results in a greatly increased tube life.

The anode 5 and the cathode 2 of the tube I may be connected by the conductors 2I and 23, in series with a load impedance I3, across a condenser I I. The condenser II may be continuously charged from a suitable source 22 of direct current, shown as a battery, through an impedance 1. The grid 3 is shown connected by the conductor 25 and a conductor II, through an impedance 28, shown as a resistor, to the positive terminal of the battery source 22. The grid 4 is shown connected to the grid 3 through a resistor or other impedance 50. It is also connected to one terminal of a condenser I5 the other terminal of which is connected to one of two signal-input terminals 55 and 51, the other of which is connected to the cathode 2. A resistor or other impedance 53 is connected between the signal-input terminals 55 and 51. The control voltage or signal is applied between terminals 55 and 51.

The condenser I I is charged from the battery 22 through the impedance 1. Though the tube l is normally non-conductive, a glow discharge is established between the cathode 2 and the grid 3, permitting the continuous flow of a small current, less than 1 milliampere, between the grid 3 and the cathode 2 from the battery 22. The voltage between the grid 3 and the cathode 2 will be determined by the glow voltage drop. In the case of a caesium cathode 2, this will be on the order of volts. This voltage will vary somewhat,

plicate with other depending upon the condition-of the surface of the cathode 2. It may range'from 9.0 to 130 volts.

Since the grid 4 is connected to the grid 3, it will assume substantially the same potential with respect to the cathode as the potential of the grid 3. Under these conditions, the grid 3 will act essentially as a supplementary cathode, used only in initiating the discharge. The voltage drop between the grid 3 and the cathode 2 will not normally affect the signal voltage required to initiate a discharge.

When a pulse of power is desired in the load impedance I3, the grid 4 is energized by a signal voltage applied between the signal-input terminals 55 and 51. When the grid 3 becomes sulficiently positive with respect to the grid 3, producing a voltage difierence of, say, about 10 volts, a glow discharge is initiated between the grid t and the cathode 2, causing the gas in the grid anode space to become partly ionized. The current first flows to the cathode 2 in the form of a glow discharge. When this current flow reaches suificient density at the surface of the cathode, a cathode spot is formed on the surface of the pill s. The action of the cathode spot causes the caesium chloride to break down, aluminum being substituted for the caesium and forming aluminum chloride. This reaction results in the formation of a thin surface layer or coating of caesium on the pill 8 and the mesh 9, which therefore together constitute part of the cathode 2. This layer has a tendency to adhere to the surface. It is on this layer that thecathode spot is formed.

A surge of current then flows from the condenser H through the load impedance l3 and the tube I, discharging the condenser ,l l. The tube l thereafter becomes extinguished, and the condenser I again becomes charged ,from'the battery 22, in readiness for the next desired surge of power through the load impedance l3.

As shown in Fig. l, the grid .39 may normally not be connected into circuit. It will nevertheless assume a potential slightly negative with respect to the grids 3 and 4, due to the presence of ions in the tube I produced by the discharge between the grid 3 and the cathode 2. This slightly negative potential permits of ahigher voltage between the anode and the grid 4 without resulting in a spontaneous breakdown between these electrodes.

In some cases, however, it maybe desirable to utilize suitable characteristics of the tube by connecting the grid 33 into circuit. The conductor 32 of the grid 33 is therefore connected to the grid 4 through a resistor 5|.

The material of the pill 8 furnishes enough free caesium so that advantage can be taken of the ease of spot formation on caesium. The formation of the cathode spot is greatly facilitated by the presence of the caesium or other material of lowwork function present on the cathode. Results are produced which are impossible to dupresent-day cold-cathode structures. The consistent formation of the cathode spot at these low gas pressures and at currents on the order of 1-5 to 20 amperes is a result, it is believed, that has never before been obtained.

Other materials than caesium chloride and aluminum may be used for the pill .8; for example, mixtures of caesium chloride and rubidium chloride and aluminum, cadmium orzinc.

The gas pressure, though relatively low, should be as high as possible to insure proper formation of the cathode spot. Helium is therefore preferred as a gas filling; its characteristics are such that, for agiven spacing of the electrodes, the gas pressure canbe much higher than for gases such as argon.

At pressures below .2 to 3 millimeters of helium, the formation of the cathode spot is apt to be quite erratic, introducing a liability of the tube to operate with a glow discharge, under a highcathode fall of potential. It is possible, however, to form cathode spots at these low pressures on the pill 8, and the tube is quite able to carry large discharge currents.

An additional advantage of the close spacing from grid to anode is to secure a short deionization time which allows operation of the tube at high frequencies. The tube is easily controlled, it .is easily operable at relatively low pressures, and there is no need to supply a source of heating power for the cathode.

,At the time of formation of the cathode spot, some caesium is sputtered on to the grid 3, thus lowering the breakdown voltage between the grid 4 and the grid 3. As the grid 4 is constituted of carbon, any sputtered caesium that may reach it will not lower the breakdown voltage from the grid 4 to the anode 5.

Since it is desired that the breakdown voltage between the grid 3 and the cathode 2 shall be substantially a minimum, the grid 3 should be spaced from the cathode 2 a distance such that the product of. this distance and the pressure of the gas in the device is represented by points of the Paschen curve for the said gas essentially to the right of its lowermost portion. As appears from the Paschen curve for helium, as shown in Fig. 6, the product of the pressure of the gas, in millimeters, and the spacing between the control electrode and the cathode 2, in centimeters, may be from about 1 to about 15. The portion of the Paschen curve between the product values above about 5 are omitted in consideration of space, but the curve starts to rise above the approximately minimum breakdown value in approximately the neighborhood of a 15 product value.

In order to obtain a substantially minimum breakdown between each of the control electrodes 3, 4 and 39 and the other control electrodes, and between each of these control electrodes and the cathode, the spacing between each of the electrodes 2, 3, 4 and 3!! and each of the others should be correspondingly designed so as to obtain operation on the same region of the Paschen curve. In the case of helium, again, the product of the spacing between the control electrodes .3 and a, in centimeters, and the pressure of the gas, in millimeters, should be from about 1 to about 15.. On the other hand, as previously explained, the spacing between the anode 5 and the grid 4 should be such as to yield a product of spacing .and pressure appreciably less than 1 thereby producing a very high breakdown voltage between the anode 5 and the grid 4. This permits the use of high anode voltages which is very desirable in many circuit applications.

Modifications will occur to persons skilled in the art, and all such are considered to fall within the spirit and scope of the invention, as defined in the appended claims.

What is claimed is:

1. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a solid cold cathode the cathode emission of which is adapted to be obtained from a small spot on the cold cathode and a control electrode spaced from the anode a distance such that the product of the said distance and pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion.

2. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and form a surface coating thereon of a material of low-work function, and a control electrode spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion.

3. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and form a surface coating thereon of a material of low-work function, a control electrode spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion, and means for maintaining a continuous glow discharge between two of the electrodes to facilitate producing an arc discharge between the cathode and anode.

4. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and form a surface coating thereon of a material of low-work function, and a control electrode spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion, and means for initiating a glow discharge between the control electrode and another electrode to produce an are discharge between the cathode and the anode.

5. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and form a surface coating thereon of a material of low-work function, and a carbon control electrode spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion.

6. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a caesium-containing solid cold cathode, and a control electrode spaced from the anode a distance such that the product of the said .distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion.

7. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a control electrode spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion, and a cathode comprising a mixture of a caesium salt and a material that will displace the caesium in the salt under the action of a cathode spot.

8. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a solid cold cathode the cathode emission of which is adapted to be obtained from a small spot on the cold cathode, and a cylindrical control electrode surrounding the anode and spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion.

9. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and form a surface coating thereon of a material of low-work function, and a cylindrical carbon control electrode surrounding the anode and spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion.

10. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and form a surface coating thereon of a material of low-work function, a control electrode spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion, and a conducting cup in which the cathode is mounted.

11. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and form a surface coating thereon of a material of low-work function, a control electrode spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion, and a conducting cup in which the said material is mounted, a wiremesh screen being disposed in the cup to cover the said material.

' will break down under the action of a cathode spot and form a surface coating thereon of a material of low-Work function, a control electrode spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion, and means for preventing breakdown between the electrodes and the other parts of the device.

14. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and form a surface coating thereon of a material of low-work function, and a plurality of control electrodes one of which is spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for 9. the said gas to the left of. its lowermost portion.

15. A gas-filled device having only three electrodes in the gas of the device comprising an anode, a cathode comprising a material. that will break down under the action of a cathode spot and form a surface coating thereon of amate- I'ial of low-work function, and a control electrode spaced from the anode a distance such that the product of the said distance and the pressure of the gas is representedby points of the Paschen curve for the said gas to the left of its lowermost portion. I I

16. A gas-fi1led device having a plurality of electrodes in the gas of the device comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and form a surface coating thereon of a material of low-work function, and a control electrode spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion, and spaced from the oathode a distance to provide substantially minimum breakdown voltage between the control electrode and cathode in the gas of the device at the pressure of the gas.

17. A gas-filled device having an envelope containing helium and a plurality of electrodes in the helium comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and form a surface coating thereon of a material of low-work function, and a control electrode spaced from the anode a distance such that the product of the said distance and the pressure of the helium is represented by points of the Paschen curve for the helium to the left of its lowermost portion and spaced from the cathode a distance such that the product of the pressure of the helium, in millimeters, and the spacing between the control electrode and the cathode, in centimeters, is between about 1% and about 15.

18. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and .form a surface coating thereon of a material of low-work function, and two control electrodes one of which is spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion and the other of which is spaced from the said one control electrode a distance to provide substantially minimum breakdown voltage between the control electrodes.

19. A gas-filled device having an envelope containing helium and a plurality of electrodes in the helium comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and form a surface coating thereon of a material of low-work function, and two control electrodes one of which is spaced from the anode a distance such that the product of the said distance and the pressure of the helium is represented by points of the Paschen curve for the helium to the left of its lowermost portion and the other of which is spaced from the said one control electrode a distance such that the product of the pressure of the helium, in millimeters, and the spacing 10' between the control electrodes, in centimeters, is between about 1 and about 15.

20. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a cathode comprising a material that will breakndown under the action of a cathode spot and form a surface coating thereon of a material of low-work function, and two control electrodes one of which is spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion and the other of which is spaced from the said one control electrode a distance to provide substantially minimum breakdown voltage between the control electrodes, the control electrodes being spaced from the cathode a distance to provide substantially minimum breakdown voltage between each of the control electrodes and the cathode.

21. A gas-filled device having an envelope containing helium and a plurality of electrodes in the helium comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and form a surface coating thereon of a material of low-work function, and two control electrodes one of which is spaced from the anode a distance such that the product of the said distance'and the pressure of the helium is represented by points of the Paschen curve for the helium to the left of its lowermost portion and the other of which is spaced from the said one control electrode a distance such that the product of the pressure of the helium, in millimeters, and the spacing between the control electrodes, in centimeters, is between about 1%; and about 15, the control electrodes being spaced from the cathode a distance such that the product of the pressure of the helium, in millimeters, and the spacing between each of the control electrodes and the cathode, in centimeters, is between about 1 /2 and about 15.

22. A gas-filled device having a plurality of electrodes in the gas of the device comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and form a surface coating thereon of a material of low-work function, and a plurality of control electrodes, one of which is spaced from -the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion, each of the control electrodes and the cathode being spaced from one another a distance to provide substantially minimum breakdown voltage between them.

'23. A gas-filled device having an envelope containing helium and a plurality of electrodes in the helium comprising an anode, a cathode comprising a material that will break down under the action of a cathode spot and form a surface coating thereon of a material of low-work function, and a plurality of control electrodes one of which is spaced from the anode a distance such that the product of the said distance and the pressure of the helium is represented by points of the Paschen curve for the helium to the left of its lowermost portion, each of the control electrodes and the cathode being spaced from one another a distance such that the product of the pressure of the helium, in millimeters, and

the spacing between the control electrodes, in centimeters, is between about 1% and about 15.

24. A gaseous-discharge device having a plurality of electrodes in the gas of the device comprising an anode, a cathode comprising a mixture, in the form of a compressed body, of a compound of a material of low-work function and a material that will displace the material of lowwork function in the compound under the action Of a cathode spot in order to form upon the surface of the compressed body a coating of the material of low-work function on which coating the cathode spot may be formed, and a control electrode spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion.

25. A gas-filled device of the Strobotron type having a plurality of electrodes in the gas of the device comprising an anode, a solid cold cathode and a control electrode spaced from the anode a distance such that the product of the said distance and the pressure of the gas is represented by points of the Paschen curve for the said gas to the left of its lowermost portion.

KENNETH J. GERMESHAUSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,679,449 Smith Aug. 7, 1928 1,731,945 Smith Oct. 15, 1929 1,760,524 Rentschler May 27, 1930 1,772,562 Foulke Aug. 12, 1930 1,939,063 Knowles Dec. 12, 1933 2,032,137 Lubcke Feb, 25, 1936 2,033,089 Bahls Mar. 3, 1936 2,125,280 Bieling Aug. 2, 1938 2,159,747 Mendenhall May 23, 1939 2,185,189 Germeshausen Jan. 2, 1940 2,192,162 Kniepkamp Feb. 27, 1940 2,201,167 Germeshausen May 21, 1940 2,416,661 Lawton Feb. 25, 1947 2,433,813 Hilliard Aug. 23, 1947 2,435,246. Stutsman Feb. 3, 1948 2,464,762 Hilliard Mar. 15, 1949 2,428,661 Fitzmorris Oct. 7, 1949 FOREIGN PATENTS Number Country Date 331,029 Germany Dec. 28, 1920 OTHER REFERENCES Industrial Electronics Reference Book, by Electronic Engineers of the Westinghouse Electric Corporation, published by J. Wiley & Sons, New York, 1948 (section 4.11, p. 55; section 6.11, p. 114). 

